Method of cutting glass



April 6, 1966 J. G. BURNS 3,247,589

METHOD OF CUTTING GLASS Filed Feb. 28, 1964 INVENTOR. JEROME G. EUR/VS 'QOmz/XM ATTORNEY United States Patent 3,247,589 METHGD 0F CUTTING GLASS Jerome G. Burns, Upper Providence Township, 1 s., assignor to International Resistance Company, Philadelphia, Pa.

Filed Feb. 28, 1964, Ser. No. 348,046 7 Claims. (Cl. 29-424) The present invention relates to a method of cutting glass, and more particularly to a method of cutting a plurality of elongated glass tubes into smaller pieces of uniform length to be used for electrical resistors. 1

In United States Letters Patent No. 2,958,899, to S. J. Stein et al., issued November 8, 1960 and entitled Apparatus for Deposition of Solids From Vapors there is described a method of making electrical resistors wherein a continuous length of glass tubing is coated on its outer surface with a resistance material. The coated glass tubing is then cut into short lengths which constitute'the active body portion of the resistors. Terminals are attached to the body portion, and they are enclosed in an insulating casing to complete the resistor. Generally, the coated, continuous length glass tube is first cut into sticks which are approximately two feet in length. The sticks are tested electrically to determine whether the resistance material coating is of the desired resistance value. The satisfactory sticks are then cut into the short resistor bodies of one-half to two inches in length depending on the size resistor being made.

There are a number of problems with regard to cutting the .sticks into the shorter pieces so as to provide good resistor bodies. The sticks must be cut so that the ends of the bodies are square, i.e., perpendicular to the longitudinal axis of the glass tube. Also, the ends of the glass bodies must not be chipped or the glass tube and resistance coating cracked. The bodies must be of uniform length to obtain resistors having the same resistance value. In addition, the resistance coating must not be damaged or contaminated, which could change the electrical characteristics of the coating. For mass production of resistors, it is desirable to be able to cut a plurality of the sticks at one time so as to reduce the cost of the cutting operation.

It is an object of the present invention to provide a novel method of cutting an elongated glass tube into short pieces.

It is another object of the present invention to provide a method of simultaneously cutting a plurality of elongated glass tubes into short pieces.

It is still another object of the present invention to provide a method of simultaneously cutting a plurality of elongated glass tubes into short pieces with the ends of the short pieces being perpendicular to the longitudinal axes thereof.

It is a further object of the present invention to provide a method of simultaneously cutting a plurality of elongated glass tubes into short pieces without chipping or breaking the short pieces.

It is a still further object of the present invention to provide a method of simultaneously cutting into short pieces a plurality of elongated glass tubes which are coated with a resistance material without damaging or contaminating the coating.

Other objects will appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others thereof, which will be exemplified in the method hereinafter disclosed, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following 3,247,589 Patented Apr. 26, 1966 detailed description taken in connection with theaccompanying drawing in which:

I FIGURE 1 is a perspective view illustrating the first step of the method of the present invention wherein a plurality of glass tubes are secured together in a bundle.

FIGURE 2 is a schematic view of an apparatus for carrying out further steps of the method of the present invention.

FIGURE 3 is a perspective view of a plurality of cut glass pieces ready for the final step of the method of the present invention.

FIGURE 4 is a perspective view of a short glass body cut from the elongated glass tube.

In general, the method of the present invention comprises arranging in closely spaced, parallel arrangement a plurality of elongated glass tubes which are coated on their outer surface with a resistance material. The arrangement or bundle of the elongated glass tubes is then placed in a container which is filled with distilled water to completely cover the glass tubes. The water is then frozen so as to encase the glass tubes in a block of ice. A saw is then passed through the block of ice and the glass tubes along planes uniformly spaced along and perpendicular to the longitudinal axes of the glass tubes. This divides the block of ice into wafer like sections each of which contains a plurality of the short glass pieces. The Wafers are then heated to melt'the ice, and the individual glass pieces are removed from the water and dried.

By completely encasing the glass tubes in ice, each of the tubes is supported around its entire surface as the saw passes therethrough so as to obtain a clean out without chipping or breaking the glass. Also, by using water as the encasing material, the water can be easily removed at a relatively low temperature and without leaving any contaminates on the resistance material coating so that there is no adverse effects on the electrical characteristics of the resistance material. Since the glass tubes are cut completely therethrough, it is possible to provide the short glass pieces with end surfaces which are perpendicular to the longitudinal axes thereof. In addition, the method of the present invention permits the simultaneous cutting of a plurality of glass tubes to obtain glass pieces of uniform length.

Referring initially to FIGURE 1 of the drawing, the method of the present invention in detail comprises first arranging a plurality of the coated glass tubes 10 in closely spaced parallel relation. As shown, the glass tubes 10 are arranged in parallel rows with a plurality of tubes in each row. This can be easily achieved by means of a suitable mechanical jig. A separate block 12 of a plastic material is cast around each end of the bundle of the glass tubes 12 with the blocks extending across and closing the ends of the tubes. Thus, the blocks 12 secure the glass tubes 10 together as a bundle, and seal the ends of the glass tubes. the ends of the glass tubes to prevent water from entering the tubes since any water within the tubes upon freezing may cause a cracking of the tubes.

Referring to FIGURE 2, there is shown a schematic illustration of an apparatus for carrying out the next step of the method of the present invention, i.e., encasing the glass tubes in a block of ice, and cutting through the ice and the tubes. The apparatus comprises a rectangular container 14 of a length greater than the length of the glass tubes 10, a Width greater than the width of the bundle of the glass tubes, and a depth greater than the height of the bundle of the glass tubes. The container 14 is open at its top, and a metal cover 16 extends across the open top of the container and is seated on the top edges thereof. The cover 16 has a U-shaped trough 18 It has been found necessary to seal extending into the container 14. The trough 18 is of a size larger than the volume of the bundle of the glass tubes. The container 14 is filled with a cooling medium 20 to a depth so that the wall of the trough 18 is in contact with the cooling medium. Although any cooling material may be used, a mixture of Dry Ice in a good heat conducting liquid, such as butyl Cellosolve or acetone, produces good results.

Mounted above the trough 18 is a flat, circular abrasive saw 22. The saw 22 is positioned in a plane which is perpendicular to the length axis of the trough 18, and is mounted on suitable mechanical means, not shown, for rotating the saw and moving it into and out of the trough as indicated by the arrow 24. Either the container 14 or the saw 22 is mounted for movement along the length axis of the trough 18 so as to permit the saw to be positioned at various points along the trough.

To carry out the method of the present invention, the bundle of the glass tubes are seated in the trough 18 as shown in FIGURE 2. The plastic blocks 12 at the ends of the bundle space the tubes 10 from the wall of the trough 18. The trough, 18 is then filled with water 26, preferably distilled water, to a level so that all of the tubes 10 are immersed in the water. The water 26 is then cooled by the cooling medium 20 until the water is completely frozen into a block of ice. To ensure that each of the glass tubes 10 is completely supported by the ice, it is necessary that the block of ice be free of any air bubbles or voids. It has been found that by freezing the water from the bottom of the trough 18 upwardly, as is achieved by the apparatus shown in FIGURE 2, the block of ice isfree of air bubbles or voids. Thus, when the water is completely frozen, each of the glass tubes 10 is completely encased in and supported by the block of ice.

When the water 26 is completely frozen, the saw 22 or container 14 is moved to place the saw over the junction of the glass tubes 10 and one of the plastic blocks 12. The saw 22 is then rotated and moved downwardly into the trough 18 so as to cut through the block of ice and the glass tubes 10. The saw 22 is then raised out of the trough 18, and either the saw or the container 14 is moved to place the saw over the glass tubes at a point spaced from the first cut equal to the desired length of the glass pieces. The saw 22 is then moved back into the trough 18 to again cut through the block of ice and the glass tubes 10. This cutting operation is continued until the other ends of the glass tubes are reached.

The above described cutting operation divides the block of ice into a plurality of waters 28 each containing a plurality of the short glass pieces 30, see FIGURE 3. The ice wafers 28 are then removed from the trough 18, or the cover 16 is removed from the container 14, and the ice is permitted to melt. The ice can be melted either at room temperature or at a slightly elevated temperature. When the ice is completely melted, the short glass pieces 30 are removed from the water and permitted to dry. The glass pieces can be dried either at room temperature or at a slightly elevated temperature. FIGURE 4 shows one of the final glass pieces 30 which is coated with the resistance material.

Thus, there is provided by the present invention a -method of cutting an elongated glass tube into a plurality of short pieces of any desired length without chipping or breaking the glass pieces and with the glass pieces having squared ends. Also, the method of the present invention permits the cutting of a plurality of glass tubes at one time. In addition, using the method of the present invention there is no adverse aflect to the electrical character'- istics of a resistance material coated on the glass tubes because of any contamination of the resistance material.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification as indicating the scope of the invention.

I claim:

1. A method of cutting a plurality of elongated glass tubes into shorter pieces comprising the steps of arranging the glass tubes in closely spaced parallel relation, then encasing the glass tubes in a body of ice which individually surrounds and supports each glass tube, and then cutting through the body of ice and the glass tubes at spaced intervals along the length of the tubes.

2. The method in accordance with claim 1 including the steps of melting the ice after the cutting step, removing the glass pieces from the water after the ice is melted, and then drying the glass pieces.

3. A method of cutting a plurality of elongated glass tubes into shorter pieces comprising the steps of securing the glass tubes together in closely spaced parallel relation, placing the glass tubes in a container which is open at its top, filling the container with water until the glass tubes are completely immersed in the water, then cooling the water until the tubes are completely encased in a body of ice, and then cutting through the body of ice and the glass tubes at spaced intervals along the length of the glass tubes.

4. The method in accordance with claim 3 including sealing the ends of the glass tubes before immersing the tubes in the water to prevent the water from entering the tubes.

5. The method in accordance with claim 4 in which the ends of the glass tubes are sealed and the glass tubes are secured together by forming a separate block of a plastic material around the adjacent ends of the glass tubes.

6. The method in accordance with claim 3 in which the water is cooled from the bottom of the container upwardly.

7. The method in accordance with claim 3 including the steps of melting the ice after the cutting step, removing the glass pieces from the water after the ice is melted, and then drying the glass pieces.

References Cited by the Examiner UNITED STATES PATENTS 2,328,302 8/1943 Simison 29-424 2,855,664 10/ 1958 Griffith et al 29-424 2,958,899 11/1960 Stein et al. 13 XR JOHN F. CAMPBELL, Primary Examiner.

THOMAS H. EAGER, Examiner. 

1. A METHOD OF CUTTING A PLURALITY OF ELONGATED GLASS TUBES INTO SHORTER PIECES COMPRISING THE STEPS OF ARRANGING THE GLASS TUBES INCLOSELY SPACED PARALLEL RELATION, THEN ENCASING THE GLASS TUBES IN A BODY OF ICE WHICH INDIVIDUALLY SURROUNDS AND SUPPORTS EACH GLASS TUBE, AND THEN CUTTING THROUGH THE BODY OF ICE AND THE GLASS TUBES AT SPACED INTERVALS ALONG THE LENGTH OF THE TUBES. 